I have an '06 G6 GT coupe that also uses the window indexing. Since we get pretty decent winter, I was concerned about problems with it, but in the long run it's been fine. I have had to run through the reset steps 2 or 3 times and once or twice they have been so frozen that it was difficult to open doors since they wouldn't index. Start the car with the remote starter, let them warm up, and it was fine.

It's odd for them to just need a reset - I think I only had to do it once after service to my alternator/battery...